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Middle Cranial Fossa
The middle cranial fossa is a butterfly-shaped depression of the skull base, which is narrow in the middle and wider laterally. It houses the temporal lobes of the cerebrum. Bones forming the fossa * Sphenoid bone, basisphenoid & greater wing of sphenoid * Temporal bone anterior to petrous ridge Content The middle cranial fossa can be divided into medial and lateral parts. In the medial part, the following structures are present from anterior to posterior: *chiasmatic groove *tuberculum sellae *anterior clinoid process *sella turcica *carotid grooves (on either sides of sella) *posterior clinoid process The lateral part is considerably deeper than the medial part to allow for the temporal lobes. Structures present in the middle cranial fossa from anterior to posterior are: *optic canal ** Transmits: CN2 with dura, arachnoid & pia, CSF & ophthalmic artery ** Formed by LWS, superomedial to superior orbital fissure *superior orbital fissure **Transmits: CN3, CN4, CNV1 & CN6 and superior ophthalmic vein ** Formed by cleft between LWS & GWS *foramen rotundum **Transmits: CNV2, artery of foramen rotundum & emissary veins ** Completely within sphenoid bone; superolateral to vidian canal ** Provides direct connection to pterygopalatine fossa *Vidian canal ** Transmits: Vidian artery and nerve ** Formed by sphenoid bone, inferomedial to foramen rotundum *foramen ovale **Transmits: CNV3, lesser petrosal nerve, accessory meningeal branch of maxillary artery & emissary vein ** Completely within GWS ** Provides direct connection to masticator space *foramen spinosum **Transmits: Middle meningeal artery & vein, meningeal branch of CNV3 ** Within GWS, posterolateral to foramen ovale *foramen lacerum **Not true foramen ** Between temporal & sphenoid bones ** Cartilaginous floor of medial part of horizontal petrous internal carotid artery canal *Carotid canal **Transmits: Internal carotid artery & sympathetic plexus ** Formed by GWS & temporal bone Relations: *anterior - posterior margins of the lesser wings of the sphenoid bone; anterior clinoid processes; anterior margin of the chiasmatic groove *posterior - anterior surface of petrous temporal bones; dorsum sellae *lateral - squamous temporal bone; sphenoidal angles of the parietal bones; great wings of the sphenoid bone *superior - temporal lobes, pituitary, cavernous sinus, Meckel cave, CN1-4, CN6, CNV1-3 *inferior - anterior roof of pharyngeal mucosal space, masticator, parotid & parapharyngeal spaces Bony features: * Sella turcica: Contains pituitary gland * Anterior clinoid processes: Extend posteromedially off lesser wing of sphenoid * Posterior clinoid processes: Extend posterolaterally off dorsum sellae; attachment for tentorium cerebelli * Chiasmatic sulcus: Just posteroinferior from posterior margin of planum sphenoidale; optic chiasm here * Tuberculum sellae: Anterosuperior margin of sella turcica Variant anatomy * Persistent craniopharyngeal canal ** Remnant of Rathke pouch ** Vertical cleft in sphenoid body at site of fusion of pre- & postsphenoid; just posterior to tuberculum sellae area in adult ** Extends from sella turcica to nasopharynx * Extensive pneumatization of sphenoid sinus ** Can cause endosinal vidian canals & foramen rotundum ** Pneumatized clinoid processes * Canaliculus innominatus ** Variant canal for lesser superficial petrosal nerve, medial to foramen spinosum * Foramen of Vesalius ** Transmits emissary vein from cavernous sinus to pterygoid plexus ** Anterior to foramen ovale